It is known to dehydrohalogenate halogen-containing compounds by reaction with aqueous alkali. Chloroprene (2-chloro-1,3-butadiene) has been prepared by dehydrochlorinating 3,4-dichloro-1-butene with aqueous alkaline solution such as aqueous sodium hydroxide or potassium hydroxide. Such a procedure is disclosed in U.S. Pat. No. 2,430,016. However, these processes are characterized by relatively low reaction rates, and relatively high yields of unwanted by-product 1-chloro-1,3-butadiene. There has been a need for a dehydrohalogenation process with a much faster reaction rate and lower yield of unwanted by-product than has heretofore been available.